Electrically conductive microemulsions based on perfluoropolyethers

Abstract

The invention relates to microemulsions of the water-in-oil type (w/o) capable of effecting ionic electric transfer and material interphase transfer, wherein the oily phase consists of a perfluoropolyether having perfluoroalkyl end groups or functional end groups of the hydrophilic type. The microemulsions are obtained using perfluorinated surfactants, in particular having a perfluoroalkylpolyethereal structure, and/or an alcohol as a co-surfactant.

What is claimed is: 
     
       1. A water-in-oil microemulsion having an electrical conductivity of at least 10 microSiemens.cm -1 , consisting of a liquid, limpid or opalescent, macroscopically monophase substance, obtained by mixing: a) water;   b) a liquid compound with perfluoropolyethereal structure having perfluoroalkyl end groups having the structure of formulas 1 to 6, with an average molecular weight from 500 to 10,000, and perfluoropolyethers of formulas 1 to 6 as herein above defined having an average molecular weight from 1,500 to 10,000, and from 0.1 to 2 non-perfluoroalkyl functional end groups for each chain, selected from: carboxyl, polyoxyalkylene-OH, alcoholic, aminic, amidic hydroxyl, quaternary ammonic ester selected from perfluoropolyethers of formulas 1 to 6: ##STR4##  with a random distribution of the perfluorooxylalkylene units, where R f  and R' f , like or different from each other, are --CF 3 , --C 2  F 5 , --C 3  F 7 , and m, n, p have such average values to meet molecular weight requirements; 2) R f  O(CF 2  CF 2  O) n  (CF 2  O) m  R' f  with a random distribution of the perfluorooxylalkylene units, where R f  and R' f , like or different from each other, are --CF 3  or --C 2  F 5 , and m and n have such average values to meet the average molecular weight requirements; ##STR5##  with a random distribution of the perfluorooxyalkylene units, with R f  and R' f , like or different from each other, are --CF 3 , --C 2  F 5  or --C 3  F 7 , and m, n, p, q have such average values to meet the average molecular weight requirements; ##STR6##  wherein R f  or R' f , like or different from each other, are --C 2  F 5  or --C 3  F 7  and n has such a value to meet the average molecular weight requirements;   5) R f  O(CF 2  CF 2  O) n  R' f  where R f  and R' f , like or different from each other, are --CF 3 , --C 2  F 5 , and n has such an average value as to meet the average molecular weight requirements; and   6) R f  O(CF 2  CF 2  CF 2  O) n  R' f  where R f  and R' f , like or different from each other, are --CF 3  or --C 2  F 5  or --C 3  F 7 , and n has such an average value to meet the average molecular weight requirements, and     c) a fluorinated surfactant.   
     
     
       2. Microemulsions according to claim 1, wherein the perfluorinated surfactant is selected from: a) the salts of the perfluoroalkylcarboxylic acids having 5 to 11 carbon atoms;   b) the salts of the perfluorosulphonic acids having 5 to 11 carbon atoms;   (c) the salts of the mono- and bi-carboxylic acids derived from perfluoropolyethers;   (d) the cationic perfluorinated surfactants or those derived from perfluoropolyethers having 1,2 or 3 hydrophobic chains.   
     
     
       3. Microemulsions according to claim 1, wherein the fluorinated surfactant is non-ionic consisting of a perfluoroalkyl chain and of a polyoxyalkylene hydrophilic head. 
     
     
       4. Microemulsions according to claim 1, wherein the perfluoropolyether exhibits functional groups along the chain. 
     
     
       5. Microemulsion according to claim 1 comprising a co-surfactant of at least one compound selected from the group consisting of hydrogenated alcohols containing from 1 to 12 carbon atoms and fluorinated alcohols. 
     
     
       6. Microemulsion according to claims 1 and 5 wherein the fluorinated surfactant is ionic. 
     
     
       7. Microemulsion according to claims 1 and 5 wherein the water contains one or more electrolytes.